Preparation And Application Of Mesoporous Carbon Molecular Sieve Membrane In Paper-likes Stainless Steel Fibers Composite

Environmental security is one of the most important concerns of mankind.As a kind of typical air pollutants,volatile organic compounds?VOCs?pose a great threat to the environment and human health.Therefore,it is an urgent problem to eliminate VOCs effectively.There are many industrial technologies for VOCs treatment,such as condensation,membrane separation,absorptive method,adsorption method,thermal oxidation,photo catalysis,catalytic oxidation.Among these ways,the valuable VOCs can be recycled by adsorption at low cost.VOCs could be decomposed to H₂O and CO₂ or other substance with lower toxicity by catalytic oxidation which needs less energy.Mass transfer of conventional fixed beds is generally worse due to their low porosity and contact efficiency.Stainless steel fibers are excellent support for adsorbents and catalysts applied to fixed bed due to its porous structure and high voidage.Poly?furfuryl alcohol?/polyethylene glycol mixture was selected as precursor,carbon molecular sieve membrane/paper-like sintered stainless steel fibers?CMSM/PSSF?was prepared via coating and carbonized process.Adsorption breakthrough curves of toluene on different structured fixed beds and operating condition was obtained.The CuO/CMSM/PSSF catalysis was prepared and applied in catalytic oxidation of toluene.Firstly,the preparation technology of polymer solution precursor was studied.The poly?furfuryl alcohol?and polyethylene were mixed and dissolved in acetone.The influence of polymer ratio and concentration on the microstructure and pore structure was studied to optimize the technology of preparing CMSM.SEM,TG,FTIR,Raman,XPS,XRD and N₂adsorption and desorption were employed to characterize different samples.N₂ adsorption and desorption tests revealed that the pore structure was changed by adding PEG in PFA and the pore size became uniform.TG and SEM results showed that the concentration of precursor should be moderate.Lower concentration was not suitable for polymer coating;nevertheless higher concentration would form agglomeration in PSSF.The temperature rating and carbonation time have little effect on the pore structure of CMSM.The pore diameter of CMSM was about 3.9 nm.The specific surface area of the CMSM/PSSF fabricated in different pyrolysis temperature varies from 26.5 m²·g^-1 to 169.1 m²·g^-1 and pore volume varies from 0.06 cm³·g^-1 to 0.23 cm³·g^-1.When pyrolysis temperature exceeds 600?,the specific surface,pore diameter and pore volume decreased as carbonization temperature increased.Besides,the degree of graphitization in carbon matrix increased with rising pyrolysis temperature.Secondly,toluene adsorption experiments on different structured fixed bed that was padded by CMSM/PSSF and granular activated carbon?GAC?were conducted.The influence of bed structure,inlet concentration and flow fate on adsorption behavior has been studied.The experiment results indicate that the toluene breakthrough curves in the adsorption bed containing CMSM/PSSF were steeper and the slope was more upright as the proportion of the CMSM/PSSF composites increased.Carbon molecular sieve membrane/PSSF composites could offer better adsorption rate,as well as mass transfer efficiency.The LUB values of structured bed constituted with 2.5cm GAC and 0.5 cm CMSM was 0.59 cm,which decrease by 10%compared to tha of fixed bed packed with 3 cm GAC.The adsorption rate constant ??was calculated by Yoon-Nelson model.The adsorption rate constant ??of structured bed was0.0328,which increased by 16.3%compared to that of fixed bed.The rate constant increased with the proportion of CMSM/PSSF.It indicates that the three-dimensional network structure and large specific surface area of CMSM/PSSF can enhance mass transfer.The adsorption rate of structured fixed bed increased while the inlet concentration and flow rate increased.Yoon-Nelson model fitted well with the expremental results and can be used for predicate the breakthrough curves of toluene.Finally,the micro-carbon molecular sieve membrane catalyst CuO/CMSM/PSSF was prepared by CVD and impregnation methods.The catalyst was characterized by SEM?XRD?N₂ adsorption and desorption?H₂-TPR and XPS.The results showed that the active component was CuO and the granular CuO was dispersed on the surface of supports.The dispersity of CuO of catalyst prepared by CVD method was better then that of impregnation method due to its higher specific surface area and better dispersion of CuO.The catalyst prepared by CVD method exhibit higher catalytic activity of toluene catalytic combustion.The catalytic activity of 10% CuO/CMSM/PSSF prepared by CVD was best;the T₅₀ was 287? and T₉₀ was 429?.The catalytic activity increased with loading amount of CuO.